I have 6 IKEA LEDBERG LEDs in my home office. I'm setting up a test PWM with just one of them. The results are odd. It only starts lighting up around analogWrite 150. Whatever value it's at, the LED gets slightly brighter/darker awkwardly. It sort of pulses slowly and randomly.
The MOSFET I'm using is a IRLB8721. I've used these plenty of times to control 12v LEDs. I'm not sure if it's the power supply or LED (or something else).
I pulled apart the LED and found 3 resistors (18 ohm, 10k ohm, 10 ohm) and 2 J3Y transistors. The transistors seem like they could be throwing things off, but I cannot make a decent educated guess in the transistor area.
The power supply is the one from IKEA @ 24v. Grounds of PS and Arduino are hooked together.
Would it make sense that these J3Ys are causing the problems? Is there any hope in dimming these suckers?
Hi,
Q1 and Q2 could be configured as constant current sources.
You need to get DMM out and reverse engineer it.
Are there any components on the other side of the PCB?
The J3Y is a manufacturer-specific short product marking (there isn't room for more!), which makes it
harder to identify the part, but if its only current control that shouldn't affect PWM dimming - I suspect
the power supply doesn't like a fluctuating load.
The range issue still exists (148 is "off" and 200 is just about as bright as 255).
But, I believe this resolved the wavering part. Keeping it at 155 for 10 seconds at a time didn't seem to show the random brightening and dimming. I'll test more tonight, but for now I have a real job I'd better keep.
